Soil contamination with explosives and their degradation products: Biomonitoring to assess sublethal toxicity in soil sentinel organisms

The Laboratory of Experimental Toxicology in CITEDEF is developing a capacity to assess toxic impact derived from environmental contamination with explosives and their degradation products. To do so, it is important to do biomonitoring that can reveal the impact on the ecosystem and predict possible consequences for the nearby population. It is necessary to develop sensitive and specific analytical methodologies for the identification and quantification of toxicants and their transformation products at low concentrations in soils and also to have biological models for the evaluation of toxic impact in situ or in the laboratory with samples from contaminated sites. In these assays, exposures would be carried out to evaluate sublethal toxicity and the absorption of aged explosives from these soils by the organisms. A possible approach to the evaluation of environmental liabilities (from a toxicological perspective) would include the study of the effects of explosives and aged byproducts in soil on target organisms representing, for example, two trophic levels (e.g. a local or model plant species and some soil invertebrate). These data can be used to define criteria or reference values for environmental management and to carry out specific risk assessments. Earthworms are essential organisms for the soil ecosystem and widely used for monitoring terrestrial systems, as they behave as sensitive indicators of soil quality against a wide spectrum of xenobiotics. In the laboratory, earthworms were exposed to explosives in order to evaluate the sublethal toxicity. These organisms would be evaluated through various measures, such as histology, histochemistry and biochemical determinations related to oxidative stress or genetic damage, as well as the identification and quantification of chemical species present in their tissues, and also water and soil samples. Experiments already carried out reflect the expected differences between explosive compounds tested in their toxic action on this organism, based on their liposolubility and chemical reactivity.